Studies outlined in this research deal with the functional and conformational properties of calmodulin. Our objective in this research is to understand the general mechanism by which calmodulin recognizes and regulates its target enzymes. We will investigate the activatio mechanism by cyclic nucleotide phosphodiesterase and myosin light chain kinase. Our basic approach is to study by flow calorimetry the changes of the enzymic activities of these two enzymes over a wide range of Ca++ and calmodulin concentrations to obtain the quantitative relationship between the enzymic activities and the concentrations of the effectors. We will assess the effects of cAMP-dependent phosphorylation of myosin light chain kinase by quantitating the changes in the enzyme activation by calmodulin. The dissociation of Ca++ from calmodulin will be studies by rapid kinetic techniques and compare to the rate of enzyme deactivation upon removal of Ca++ to determine the stoichiometry of Ca++ in the activated enzyme complex. The rate of Ca++ dissociation will also be used to monitor changes in the structure of the Ca++ binding sites on calmodulin upon bindings of enzyme, trifluoperazaine, TNS and ACTH (1-24). We propose to enrich the methiorine residues in calmodulin with 13C and investigate the local environment of these residues with 13C NMR and to monitor the changes in the environment associated with the binding of Ca++ trigluoperazine, TNS and ACTH to calmoduin. Results obtained from the present study should increase our understanding of calmodulin-mediated processes in general and the structure-function relationship of this important regulatory protein.